Preventing Sirmium's decline



What caused the relatively important late Roman imperial city of Sirmium, in modern Serbian Slavonia, to decline sharply, and effectively disappear during Avar times? What made it so important (enough to warrant diocese capital status) in the eyes of the emperors?
How can the decline of this city be prevented? Bonus cookie points to those who manage to save the city after Attila's arrival.
 
Love the fact that there are two regions, “Perfectures,” of the late W. Roman Empire that I’ve never heard of! :)

And wish I knew more about this period.
 
Wasn’t it razed to the ground by the Avars? That would do a number to any city
It was sacked by the Huns in 442, and then utterly destroyed by the Avars in 582.
What caused the relatively important late Roman imperial city of Sirmium, in modern Serbian Slavonia, to decline sharply, and effectively disappear during Avar times?
The fact that they razed it to the ground.

What made it so important (enough to warrant diocese capital status) in the eyes of the emperors?
Look at its location. It's a key strategic point right near the Danube border and acted as a staging point for military campaigns (notably Marcus Aurelius's Marcomannic War and Trajan's invasion of Dacia. It was also a key point in the Gothic wars of the 3rd century). Because of that strategic location it basically became the base of operations for campaigns in that theater, hence its status in Diocletian's system.

How can the decline of this city be prevented?
Have it not be sacked?

Bonus cookie points to those who manage to save the city after Attila's arrival.
Have the Avars not sack it, and have the Eastern Roman Empire maintain control over that area.
 
To add to Sly's point, the location might not much use except as a staging ground for the armies of a Mediterranean empire hoping to project power into the regions beyond the Danube.

Thus you need a Roman Empire type state to want it to endure.

Plenty of sacked cities come back. This one didn't. I'd wager it in part had to do with a lack of imperial patronage.
 
It all depends on why it survives and thrives. Do the Slavs not penetrate into the Balkans because the Romans handle the Avars better (hence no sack)?
I think it can survive being sacked, whether that means the Slavs are held out of the Balkans is another matter.
One of the theories OTL is that Moesia proved enough of a haven for Romance speakers despite the Slav migration that it enabled their ingress back into Dacia and the lowland-highland split of Slavic and Romance languages across the northern Balkans.
 
Sorry for not excellent English
First of all - Sirmium continued to exist at least at 630-ths
We know that Hieracklius stayed a harrison in Sirmium after victory in Persian war
At this time Romans tryed to reestablish Danube limes
But then Arabs came - and Romans did not spand their resourse for Balkans
 
Sorry for not excellent English
First of all - Sirmium continued to exist at least at 630-ths
We know that Hieracklius stayed a harrison in Sirmium after victory in Persian war
At this time Romans tryed to reestablish Danube limes
But then Arabs came - and Romans did not spand their resourse for Balkans
Would having the Byzantines beat back the Bulgars early be sufficient a PoD for Sirmium to recover?
 
Alternatively, we could have an "Exceptional" - i.e. someone like Odaenathus to protect Sirmium, or perhaps avoid the attempt to reconquer Africa from the Vandals that created the opening for the Huns in the first place - instead choosing a more moderate strategy - perhaps using Illyria to rebuild the fleet, or even focusing on conquering the lands around Sirmium, with the intent of having a large, secure territory that could be more easily defended in the future.
 
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